Hereditary hemorrhagic telangiectasia (HHT), is an autosomal dominant condition causing recurrent epistaxis, telangiectasias and visceral vasular anomalies. Its true prevalence is not known with reports ranging from 1:2, 351- 39, 216 with the prevalence in Vermont to range between 1: 8,000- 16,500. Recently this investigator and collaborators have found that HHT actually occurs as a family of similar conditions: HHT I, caused by a defect in endoglin alpha transformining growth factor- beta receptor on chromosome 9; HHT II caused by an as yet unidentified gene on chromosome 12; and other forms caused by other unidentified genes. Currently, there is little information available regarding the natural history of HHT especially of the type needed to distinguish among the genotypic forms of HHT. This proposal is part of an international collaborative study which will gather detailed information regarding the natural history of HHT in a thousand individuals with the disorder. As genotypic information increases from these families, repeated analysis will be carried out to achieve a reliable genotype- phenotype and mutation-phenotype correlations. Such information will allow for optimal management of individuals with this disorder and add to the basic understanding of the pathophysiology of HHT and other vascular phenomena. This study utilizes self-administered questionnaires to gather data about the natural history of HHT that has been developed by a consortium over a dozen international centers involved in research and clinical of HHT with results tabulated and computerized at the GCRC at UVM in collaboration with the Clinical Research Center at Yale University. The HHT foundation has already sent questionnaires with cover letters to each of its 386 non-physician/scientist members. As of December 1, 1996, over 340 individuals previously diagnosed with HHT completed and returned questionnaires about themselves. Another 50 questionnaires about living children and 25 about deceased relatives had also been received. Data input, tabulation, & analysis is being performed with use of the CDMAS facility. Preliminary data from the questionnaires was presented at the Rendu Centenary Meeting in Edinburgh, Scotland in May 1996, and at the HHT Foundation Annual Meeting in Salt Lake City, UT in July 1996.